A strange creature, half robot, half rat, has been seen scuttling across a laboratory in Japan. It's RatCar, a rat-vehicle experiment that scientists hope could lead to improved mobility for people with disabilities.

"We wanted to develop a brain-machine interface system aiming for future wheelchairs that paralyzed patients can control only with thought," says Osamu Fukayama of the university's Medical Engineering and Life Science Laboratory. "RatCar is a simplified prototype to develop better electrodes, devices, and algorithms for those systems."

In the RatCar, tiny neural electrodes [the dark dots on the tip of the device shown on the photo, right] were implanted in the motor cortex of rat brains, and the animals were suspended under a lightweight, motorized "neuro-robotic platform" with wheels. The objective was to make the vehicle collaborate with the rats to achieve the locomotion they desire.

The rats were trained on the car by towing it around an enclosed area with the motors disengaged. A vision system positioned above tracked the rats by following colored markers on their backs and the vehicle. It fed the positions into a "locomotion estimation model" program that correlated the motion of the animals with readings from the electrodes.

Next the rats were suspended more tightly to the car so their limbs touched the floor only slightly. The researchers then switched the system into "neuro-robotic mode," with the neural signals used to help drive the car. Six out of eight rats used in the study adapted well to the car.

"The vehicle moved forward synchronously with a rat when it was placed inside," says Fukayama, but he adds that the degree to which the car was being controlled by the rat itself was unclear.

Since the rat would be forcibly moved along with the car, measuring its real intentions became a challenging problem. Another difficulty was that only a small percentage of the electrodes actually recorded neural activity, and the recorded neurons didn't necessarily correlate with target movements.

Fukayama and colleagues Takafumi Suzuki and Kunihiko Mabuchi plan to perform more experiments to address the uncertainties. They want to confirm that the rats can drive the car in different directions and also measure the force that the rats are exerting when trying to move under the car. That way, they could track differences in its motion and the rats' apparent intentions.The less force, the better the neural link is working.